ServerName: Make it your default server name.
DefaultRoot: Uncomment this line to restrict users with their home folders.
AuthOrder: Uncomment the line to enable the using of local passwords.

Checking the syntax of the configuration file

# proftpd -t6

Users Authentication Configuration

When you install ProFTPD, it is almost ready to use by anonymous users, you only have to uncomment anonymous section in /etc/proftpd.conf but if you want authenticated access then you must configure extra directives, keep in mind these to virtual users authentication.

AuthUserFile : Specify the users file, has the same format as /etc/passwd
AuthGroupFile : Specify the groups file, has the same format as /etc/group